Down draft oil burner



March 15, 1955 H. c. LITTLE 2,704,118

DOWN DRAFT OI-L BURNER Original Filed Nov. 20, 1944 WZ Z.

United States Patent-O DOWN DRAFT on. BURNER Harry C. Little, San Rafael, Calif.

Original application November 20, 1944, Serial No. 564,290, now Patent No. 2,473,653, dated June 21, 1949. Divided and this application May 23, 1949, Serial No. 94,763

4 Claims. (Cl. 158-91) This is a division of my copending application Serial No. 564,290 filed November 20, 1944, now Patent No. 2,473,653, issued June 21, 1949. The invention relates to a liquid fuel burner and more particularly to an oil burner such as disclosed in my pending application Serial No. 535,321, now Patent No. 2,483,978, issued October 4, 1949, wherein the burner parts are so arranged that the vaporized fuel mixture leaving or preparing to leave the fuel generating chamber is caused to burn in a zone defined, at least in part, by a heatradiating element located directly within the chamber and shielding the interior from contact with the flame, the element serving by reason of the intense heat communicated to it by the flame, and transmitted by the element to the interior of the chamber, to produce a thorough vaporization of the liquid oil and a thermal cracking of the vaporized fuel to an extent that more volatile and highly combustible components are produced in the chamber without the attendant production of elemental carbon or soot, and at the same time due to the positioning of the element and the associated parts of the burner, the said components on departing from the chamber and moving through said burning zone, the throat, and the combustion chamber, will be readily consumed to provide a most efficient flame.

An object of the invention is to provide a burner of the character described, in which the heat-radiating plate is so arranged in the generating chamber that a maximum quantity of fuel mixture will be most efiectively subjected to the effect thereof for producing a mixture capable of sustaining a high-temperature, soot-free flame.

Another object of the invention is to provide a generator of the character described, in which the heat-radiating element is so arranged in the generating chamber that a thorough admixture of the vaporized oil and air will be permitted in the chamber, and practically all such mixture will be distributed to insure a uniform and effective action thereon by the element.

A further object of the invention is to so design and arrange the heat radiation element that it may be effectively incorporated in burners having fuel vaporizing and mixing chambers of either elongated, cylindrical, or other form.

A still further object of the invention is to provide an effective arrangement for insuring the heating of the radiation element to a relatively high temperature.

Additional objects will be apparent from the present description considered together with the accompanying drawing wherein the preferred embodiment of the invention is set out. It is to be understood, however, that modifications and variations from these particularly illustrated applications of the inventive concept may be made without departing from the spirit of the present teaching.

Referring to said drawing:

Figure 1 is a vertical sectional view through a down draft type of burner, while Figure 2 is a plan view of the same burner with portions of the top cut away to reveal the interior construction.

As above explained, the novel means of my invention includes a heat radiating element 41 which may be so designed as to adapt it for incorporation in various types of oil burners, particularly in respect to the generating chamber, that is, the chamber or space in whichthe oil is vaporized and mixed with primary air. In Figures 1 and 2, the said means of my invention is illusice trated in connection with a burner, having a cylindrical casing 43, which defines a generating chamber 42. At the lower portion of the casing 43 there is provided the burner throat 44 to provide a down-draft type of burner construction. Oil in liquid form may be supplied to the vaporizing chamber through a suitable side inlet opening adjacent the bottom of the burner, the oil being admitted through a pipe 56 so as to provide a pool on the bottom. The level of the oil may be controlled by a suitable float valve 13', and ignition for starting may be effected by any suitable conventional means.

Primary air to the generator is admitted through perforations 47 provided in the side walls of the casing, and the supply of such air may be augmented by means of additional openings 48 and and 49 which supply secondary air for low-fire operation and primary air for high-fire operation, and preferably openings 50 are formed in the walls to provide air jets for impinging on the skirt 51 of the heat radiating element 41.

The secondary air for the throat is provided by a passage 52 between the bottom of the generating chamber casing 43 and the bottom 53 of the casing housing 54. Air may be supplied, and, if desired, under force feed, through a duct 57.

The heat-radiating element 41 is of generally annular form and is positioned adjacent the top of the casing and is substantially vertically aligned with the throat 44. As will be clear from Figure 1, the space between the element 41 and the bottom of the generating chamber is relatively large as compared to the space 45 between such element and the top of the casing, and preferably the space 46 between the periphery 51 of the element and the sides of the casing corresponds with the space 45. In this down-draft arrangement a throat extension in the form of a tube 58 of frusto-conical form is provided between the plate 41 and the throat opening at the bottom of the generating chamber, in order to provide for the passage of the products from the lowfire burning zone to the throat. If desired, and as here shown, the tube and plate may be formed as integral members, the tube thus forming an extension of the plate and functioning to heat the vapor and air mixture in the generating chamber. As will be understood, when the burner is in operation, the gas mixture from the generator chamber will be drawn through passages 45 and 46 into the tube 58 and thence to the burner throat, and in order to provide for a burning zone in space 45 the openings 48 are formed in the sides of the casing to furnish what at least at low-fire operation serves as secondary air. Likewise the relatively large concentration of openings 50 are formed below'the openings 48 so as to provide flame jets designed to impinge directly upon the element during the operation of the burner and thus insure the element being heated to a red hot state. The radiation element or baflle is fabricated of heat conducting material, preferably such as iron, stainless steel, etc., or other suitable metal or alloy.

On ignition of the mixture in space 45, the element 41 will become heated over its entire area and thereby cause an intense radiation of heat thereform directly to the gases in the space between the plate and the bottom of the casing. In this manner, the oil in the generating chamber will be quickly and effectively vaporized and combined with the air, and as the tempo of combustion increases and the radiation element becomes hotter the rate of passage of air and vaporized fuel through the mixing chamber and adjacent the radiation element will increase correspondingly. On the other hand, the radiation element apparently cracks or decomposes (at least part of) the fuel oil vapor into more volatile hydrocarbons, since the flame produced in the combustion zone resembles that of natural gas. When it is stated that the radiant element actuates the vaporized fuel, this term is intended to include both the action of thermally cracking some of the gaseous hydrocarbons and the action of imparting energy to these and other gaseous hydrocarbons which renders them more susceptible to combustion and/or to subsequent cracking upon entering the burner throat or combustion zone. It will be evident that, owing to the relatively great expanse of the radiating element, a large spread of the fuel mixture will be provided before the mixture can pass into the burning zone in the space 45, so that not only will a thorough mixing of the-vapor and air be produced, but an intimate contact of all of the mixture with the radiating plate will be assured, and the peripheral flange 51 is provided around the radiating plate in order to increase said action.

It is important to note that, by reason of the relatively restricted cross-sectional area of the spaces or passages 45 and 46, the flow of the mixture will be ap preciably reduced in volume, and since the supply of air from the openings 48 will continue uninterrupted, the ratio of the'air to the fuel will be increased, thereby insuring the most effective burning of the partially cracked oil vapor. Furthermore the streams of air from openings 48 directed completely around and straight into passage 45 provide for a thorough injection and penetration of the air in the mixture admitted to the passage and in this way the effective burning is additionally assured.

The effective low-fire burning, as above described, is extremely important for the economical operation of the burner, and at the same time the arrangement is such that the burner is very efficient for high-fire operation, for while the burning zone on high-fire operation moves high up into the throat and combustion chamber, the efficient vaporization of the fuel and the conditioning of the mixture is maintained. As will be apparent to those skilled in the art, the relationships and sizes of the various parts, chambers and passages are of utmost importance in providing a burner which will operate in the effective manner hereinabove set forth, and while I have not given any dimensions for the parts, passages, etc., in the drawings,-I have found that the burner when constructed with such parts, etc., in the proportions shown in the drawings will provide for efficient operation with most liquid fuels.

In actual practice, the burner when provided with the radiating plate and arrangement of my invention, as compared to a corresponding burner without the element, will operate with equal effectiveness with onethird the draft, and will have an oil burning capacity far greater. Furthermore, the burner with my element will have a CO percentage far greater than a corresponding burner without the element. In addition, the present burner will burn with a transparent, blue-white flame and without free carbon while the burner without the element under the same conditions will burn with a yellow flame and produce free carbon. over, in my burner there is no burning below the radiating plate, and no products of combustion are present in the primary mixture, as the activation produced by the radiation plate converts the vapor and the mixture in the more volatile gases, from which practically all free carbon is absent. On the other hand, without the radiating plate, partial combustion will take place in the generating chamber and products of combustion will mix with the primary mixture of the vapor and air, a condition which is most undesirable.

I claim:

1. A liquid fuel burner including means defining a fuel vaporizing and air mixing chamber provided with upper and lower parts and air inlet means in its sides, means for delivering a regulated amount of liquid fuel over said lower part, means in said bottom part providing a burner throat having a tubular extension projecting upwardly into the chamber adjacent the top part, a heat radiating plate at the top of said extension extending from the sides thereof to adjacent the sides of the chamber to form an annular restricted passage between the plate and upper part and between the peripheral edges of said plate and said sides, and air inlet means in substantial axial alignment with said tubular extension arranged to direct air from the exterior to the interior of the chamber at said restricted passage.

More- 2. A downdraft liquid fuel burner comprising means defining an outer chamber adapted for receiving air under pressure and having a horizontally disposed base with a central opening therein, means defining an air mixing and fuel vaporizing chamber situated within and spaced from, and having air inlets in its side and top walls communicating with said outer chamber and including a horizontally disposed base having a central opening therein, means for delivering a regulated amount of liquid fuel to the lower part of said vaporizing chamber, a frusto-conical burner throat made of heat-conducting material centrally positioned in said vaporizing chamber and having an upper aperture adjacent the upper part of said vaporizing chamber and a lower aperture at the base of said vaporizing chamber in communication with said opening in the latter, a bafile of heat conducting material laterally extending from the upper part of said throat and adjacent said upper aperture nearly to and at approximately a right angle to the side walls of said vaporizing chamber, the base of said vaporizing chamber being positioned above the base of said outer chamber forming a space in flow communication with said air under pressure to permit the passage of secondary air from the outer chamber into said throat adjacent said lower aperture and said opening in said outer chamber.

3. A downdraft liquid fuel burner comprising means including a base defining an outer chamber adapted for receiving air under pressure, means including a base spaced from said outer chamber and defining an air mixing and vaporizing chamber situated entirely within in spaced relation to, and having air inlets in its side and top walls communicating with, said outer chamber, tubular means forming a burner throat and made of heatconducting material centrally positioned in said vaporizing chamber and having an aperture at the upper end adjacent the top of the vaporizing chamber and a second aperture adjacent said base of the vaporizing chamber and in communication with an opening formed in the bottom of the vaporizing chamber, a baffle of heat conducting material extending from said tubular means adjacent said upper aperture nearly to and at approximately a right angle to the side walls of said vaporizing chamber, said outer chamber base having an opening in alignment with the opening in said vaporizing chamber base said base of said vaporizing chamber being positioned above said base of said outer chamber to permit the passage of secondary air from the outer chamber into said throat adjacent said lower aperture.

4. In a downdraft liquid fuel burner, side, top and bottom walls defining a fuel vaporizing and air admixing chamber provided with a plurality of air inlets in the side walls, said bottom wall being provided with a central opening defining in part a burner throat, a tubular member extending from said bottom Wall and in flow communication with said central opening to adjacent said top wall, a heat conducting plate mounted at the top of said tubular member and substantially equally spaced from said side and top walls to define a restricted passage leading from the chamber into the tubular member, and means defining an air inlet in said top wall overlying the upper end of said tubular member.

References Cited in the file of this patent UNITED STATES PATENTS 440,038 Jarmain Nov. 4, 1890 497,490 Calkins May 16, 1893 990,150 Liddell Apr. 18, 1911 1,761,537 Ravenor June 3, 1930 2,137,681 Adolfson Nov. 22, 1938 2,260,548 Veghte Oct. 28, 1941 2,418,709 I-Iayter Apr. 18, 1947 FOREIGN PATENTS 793,451 France Nov. 23, 1935 

